First is the quality of the storage device. You cannot buy a cheap counterfeit product on the streets and expect it to be genuine. The truth is those devices sold cheaply by street vendors and even some shops have a reason of such cut in price and the main reason behind it is it is either fake or from a non-genuine manufacturer. To avoid this always go with the most trusted brands like San Disk, Toshiba, Sony or that you are familiar with and buy from authorised dealers. Quality products may cost but it pays to get quality service.
Finally the storage device maybe infected with a malware or virus and therefore needs a thorough scanning. Avoid using your storage devices in unknown laptops and phones and always do an antivirus scan before opening any folder in the device. Catching the flu virus when your friend is just the same as storage devices with malware infected computers or phones. Prevention is better than cure!